Dupixent Lawsuit Filed After Mycosis Fungoides Diagnosis

A new lawsuit ties Dupixent (dupilumab) to a diagnosis of mycosis fungoides, the most common form of cutaneous T-cell lymphoma, in a male patient who took the blockbuster biologic.

The complaint, reported by AboutLawsuits.com, was filed against the drug's manufacturers and alleges the man developed mycosis fungoides — a slow-growing lymphoma that first appears in the skin — after treatment with Dupixent. The case now joins the broader wave of product-liability litigation over the IL-4/IL-13 inhibitor.

What is the plaintiff alleging?

The core claim is failure to warn. The man's legal team argues the manufacturers knew, or should have known, about a link between dupilumab and cutaneous malignancy, and that patients and prescribers were not given adequate warning of the risk.

Mycosis fungoides is the diagnosis at the center of the suit. For dermatology clinicians, that detail matters. The condition typically presents as persistent patches and plaques, often mistaken for eczema or psoriasis before biopsy confirms the lymphoma — a diagnostic overlap that complicates both clinical practice and causation arguments in court.

Dupixent is approved for atopic dermatitis, asthma, chronic rhinosinusitis with nasal polyps, eosinophilic esophagitis and other type 2 inflammatory indications. It remains one of the highest-revenue drugs in dermatology.

What does this change for prescribers?

Right now, nothing formal. A filed complaint is an allegation, not a finding. No verdict has been reached, and the litigation has not altered the drug's label.

But litigation pressure has a way of moving upstream into prescribing habits. Clinicians who manage severe atopic dermatitis on dupilumab may see patients asking about cancer risk at their next visits. Having a clear, evidence-based answer ready — what the label says, what trial and post-marketing data show — is now part of the job.

It's also worth remembering why mycosis fungoides gets misdiagnosed so often: it mimics the very diseases Dupixent treats. A patient whose "eczema" fails to respond, or whose lesions evolve in morphology, warrants biopsy rather than another biologic escalation. That clinical instinct protects patients regardless of how the lawsuits turn out.

The road ahead

The case will proceed through discovery, where internal manufacturer documents on signal detection and pharmacovigilance typically become the battleground. Whether courts allow the litigation to consolidate into a multidistrict litigation — and whether the science holds up under Daubert scrutiny — will determine its real weight.

For now, dermatologists should watch the docket, keep informed-consent conversations current, and treat any suspicious lesion in a dupilumab patient exactly as they would in any other: with a biopsy, not an assumption.